The effects of a cholecystokinin peptide (CCK) in the central nervous system regulation of eating behavior is studied in sheep. The hypothesis that CCK in the brain is released into cerebrospinal fluid during feeding and travels to receptor sites involved in satiety is tested using lateral ventricular injections of antiserum to the peptide. Feeding responses resulting from the binding of the peptide with the antibody are evaluated. A dose response relationship for feeding elicited by use of the antiserum is also determined.